package com.lishem.leftgod.level1.class04;

/**
 * 在二叉树中找到一个节点的后继节点
 * <p>
 * 现在有一种新的二叉树节点类型如下：
 * public class Node {
 * public int value;
 * public Node left;
 * public Node right;
 * public Node parent;
 * public Node(int data) {
 * this.value = data;
 * }
 * }
 * 假设有一棵Node类型的节点组成的二叉树，树中每个节点的parent指针都正确地指向自己的父节点，
 * 头节点的parent指向null。只给一个在二叉树中的某个节点node，请实现返回node的后继节点的函数。
 * 在二叉树的中序遍历的序列中，node的下一个节点叫作node的后继节点。
 */
public class Code_07_DescendantNode {

    private static Node getNextNode(Node node) {
        if (node == null) {
            return null;
        }
        if (node.right != null) {
            node = node.right;
            while (node.left != null) {
                node = node.left;
            }
            return node;
        }
        Node parent = node.parent;
        while (parent != null && parent.left != node) {
            node = parent;
            parent = node.parent;
        }
        return parent;
    }


    public static class Node {
        public int value;
        public Node left;
        public Node right;
        public Node parent;

        public Node(int data) {
            this.value = data;
        }
    }

    public static void main(String[] args) {
        Node head = new Node(6);
        head.parent = null;
        head.left = new Node(3);
        head.left.parent = head;
        head.left.left = new Node(1);
        head.left.left.parent = head.left;
        head.left.left.right = new Node(2);
        head.left.left.right.parent = head.left.left;
        head.left.right = new Node(4);
        head.left.right.parent = head.left;
        head.left.right.right = new Node(5);
        head.left.right.right.parent = head.left.right;
        head.right = new Node(9);
        head.right.parent = head;
        head.right.left = new Node(8);
        head.right.left.parent = head.right;
        head.right.left.left = new Node(7);
        head.right.left.left.parent = head.right.left;
        head.right.right = new Node(10);
        head.right.right.parent = head.right;

        Node test = head.left.left;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.left.left.right;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.left;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.left.right;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.left.right.right;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.right.left.left;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.right.left;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.right;
        System.out.println(test.value + " next: " + getNextNode(test).value);
        test = head.right.right; // 10's next is null
        System.out.println(test.value + " next: " + getNextNode(test));
    }

}
